Alkoxy benzene in froth flotation process



ALKOXY BENZENE IN FROTH FLOTATION PROCESS Roger F. Powell, Gwelo, Southern Rhodesia, and Eric F. Martin, Germiston, Transvaal, Union of South Africa, assignors, by direct and mesne assignments, to National Chemical Products Limited, 'Germiston, Transvaal, Union of South Africa No Drawing. Application August 2, 1954, Serial No. 447,441

Claims priority, application Great Britain June 14, 1949 8 Claims. (Cl. 209-166) the mineral pulp, said alkoxy benzene compound acting as a frother and improving the resulting flotation operation in the separation of the minerals from the impurities associated therewith.

The froth flotation processes of the present invention are particularly suitable for the concentration of noble and base metal ores and provide for a Wide range 'of frothers for selection under the best conditions for the treatment of widely varying mineral compositions.

The froth flotation agents of the present invention are particularly adapted for the treatment of pyritic ores or cyanide slime plant residues of the type where recovery by flotation has pres'entedgreat difl iculties using the methods hereto available. The present frothers are likewise suitable for use with ores containing tarnished pyrite, chaicocite, and ores of the complex lead-zinc'type.

The flotation process of the present invention may be used with good advantage in the treatment of gold ores containing small amounts of sulfides or arsenides, the bulk treatment of copper ores containing siliceous gangue and the treatment'of ores in which two or more base metals are to be separated from each other, such as copper, lead, zinc or the like. The process may likewise be used for the separation of coal, for instance, of the coking and non-coking type.

The alkoxy benzene compounds of the present invention include benzenes substituted with at least one and up to four alkoxy substituents, the benzene ring -bei ng connected to the alkoxy substituentby an ether COC linkage, alkoxy being selected from the group consisting of methoxy, ethoxy, normal propoxy, isopropoxy, methoxy-ethoxy and ethoxy-ethoxy. "it is preferred touse alkoxy benzene froth flotation agents which are substituted with at least two of such alkoxy groups. The alkoxy benzenes includes the dialkoxy ben'z'enes, trialkoxy 'benzenes and tetraalkoxy- 'benz en'es. The "tetraalkoxy benzene may be 1,2,3,5 tetrameth'oxy benzene. The trimethoxy benzene may be 1,2,3 trimethoxy benzene or 1,3,5 trimethoxy benzene or 1,2,3 triinethoxy benzene. The dimethoxy benzenes may be the ortho, meta or para isomers.

Generally, all of the isomers of the di, tri and tetra alkoxy benzenes, alkoxy as above defined, are each equally suitable within any particular'substitution class and as will be evident from the more detailed description set forth below.

The dialkoxy benzenes are prepared-"by conventional procedures and are also available commercially. The

trialkoxy benzenes are prepared in conventional manner" by the alkylation of the corresponding trihydric phenols such as phloroglucinol, pyrogallol, etc.

are formed, the benzoquinones are then reduced to the benzohydroquinone and the later alkylated to add on the two alkoxy grou s to the hydroquinone derivative and produce the desired product. For example, 1,2,3,5 tetramethoxy benzene is obtained by oxidizing pyrogallol trirnethyl ether to 2,6 dimethoxy benzoquinone, the latter reduced to 2,6 dimethoxy benzohydroquinone whereafter methylation with dimethyl sulfate in 20% aqueous NaOH and in the absence of air produces the desired 1,2,3,5 tetrarnethoxy benzene.

sired alkoxy substituents.

It is convenient to summarize the essential properties: or frothers of interest in froth flotation processes, when used in conjunction with any of the commonly known promotors and or conditioners, as follows:

i. That a small quantity of the frother per unit quantity of the ore or other material treated shall sufiice to obtain the desired effect.

ii. Rate of dispersability of the frother in an aqueous ore or like pulp to which it is added.

iii. Carrying or collecting powera term already understood in the art.

iv. Selectivity of the frother in its action upon the different minerals or other substances in association with one another inv the pulp or the like, each of which having to be floated and, as far as possible, floated separately.

v. Selectivity of the frother in its action as between minerals or other materials which it is desired to float, and gangue or the like which it is desired not to float.

vi. Persistence of the frother in recirculation.

Adverting to the feature that organic compounds embraced within the range herein set forth and utilizable individually as elfective frothing agents, are readily miscible with one another with the important result that means are thereby afforded in flotation practice enabling the frother by selective mixture to be varied in such a way as to combine in desired proportion essential properties each possessed by the individual substances in different degrees to suit special characterization of a given ore, coal or other material to be treated, this aspect of the present invention will now be more fully discussed.

From a knowledge of the particular flotation properties of individual species in the range of compounds herein set forth, blends of any two or more of these substances can be produced with predictable flotation properties.

Advantages accruing from the aforegoing are very substantial, as will appear from the following:

1. Large quantities of cheap species can be blended with smaller quantities of expensive species for economic reasons;

2. Species, one or other of whose properties exclude or substantially exclude them from the range of practical'effectiveness when used alone, can be combined to bring such properties within the useful range by intelligent blending of such species with one another.

Adverting to the discussion of the principal practical properties of any frother as appearing earlier herein- 'i. Sel ctivity as between two or more valuable minerals which are required to be floated as far as possible separaiely.This property of selectivity is substantially in- Patented Jan. 8-, 1957 The tetraalkoxy' benzenes may be prepared through oxidation of the cor-- responding trialkoxy compounds whereby benzoquinones The other alkoxy derivatives may be prepared in like manner, the alkylating agent being; modified as is well known in order to introduce the de-- ii. Deleterious tendency to float valueless ganglia with valuable minerals.-It has already been established that this tendency is possessed by those species in which the alkoxy group is isopropoxy. Also there is little, if any, increase in this deleterious property as one increased the number of any specific alkoxy groups in the molecule.

For the flotation treatment of particular ores and the like, specific frothers may thus be produced by blending suitable members of the series having regard to the foregoing. As is well known, three main types of ore are 10 met with, namely base metal, e. g. copper, in which case while maximum economic recovery is naturally highly desirable it is absolutely essential that the minimum of siliceous gangue shall be present in the final concentrate.

TABLE I.--SlANDARDISED PRELIMINARY WATER-FROTHING TEST ON A NUMBER OF POTENTIAL FROTHERS [Long experience has shown that this test gives a very fair indication of the comparative behavior of potential frothers, roughly quanitatively. Net commercial strength and qualitative properties have to be determined on actual ores] Approximate Quantity Approximate needed to Quantity Formula of Compound Physical State start good needed for froths (withfroth to out viscosity Run Over correction) 1. (I) CH3 0 CH3 Liquid 0.09 cc 0.24 cc.

2. (I) OH:

Liquid 0.22 cc 0.36 cc.

Solid; used 10% 0.26 g 0.41 cc.

w./v. in alcohol.

Solid; used 5% 0.05 g 0.07 g.

w./v. in alcohol.

OOH: Solid; used 50% 0.045 g 0.105 g.

W./v. in alcohol.

--O CH:

PINE 0IL Liquid 0.057 cc 0.114 cc.

0 02115 O CgHs I t I i t HC-(iJCIl?-(l3-?H Liquid 0.015 00 0.030 cc.

I H H H H H 0 01H;

0 C1H O CgHs i H-C-(|J (JH Qommercial Liquid 0.045 on 0.075 cc.

1 H H H 1 All soluble with great ease in pure 1:1:3-triethoxybutane or Commercial 1:1:3 Triethoxybutane. V I

(c) Ores in which minerals'of two or more base metals are to be separated as far as possible from each other as well as from the gangue; in which case the desiderata are extreme selectivity coupled with deep and powerful froth While at the same time maximum carrying-power is desired in the second or final stage of flotation.

As regards coal separation the first desideratum is extreme selectivity to permit the separation of two or more basic types of coal, as for instance, coking and noncoking coal.

An object of the invention is to provide improved froth flotation agents for the flotation of mineral pulp which alone or in various combinations with members of the specified class, polyalkoxy benzenes, alkoxy defined as selected from the group consisting of methoxy, ethoxy, normal propoxy, isopropoxy, methoXy-ethoxy and ethoxyethoxy provide improved selectivity and improved flotation results to satisfy the requirements indicated hereinabove.

A further object of the invention is to provide a method for concentrating minerals by flotation comprising adding to the mineral pulp a small quantity of a polyalkoxy substituted benzene as a frother, the 'alkoxy groups being connected to the zenzene nucleus by a C'OC ether linkage and alkoxy being selected from the group consisting of methoxy, ethoxy, normal propoxy, isopropoxy, methoxy-ethoxy and ethoXy-ethoxy and thereafter subjecting the resulting mixture to a flotation operation.

Other and further objects of the present invention will appear from the more detailed description set forth below, it being understood that such detailed description is given by way of illustration and explanation only and not by way of limitation, since various changes therein may be made by those skilled in the art without departing from the scope and spirit of the present invention.

EXAMPLE 1 Standard water frothing test A 5% solution of the following polyalkoxy benzenes are prepared in ethyl alcohol (absolute) and these 5% solutions were added in the amounts specified in Table I below in order to determine the amount necessary to start a good froth and the amount necessary to make the froth run over, these amounts being placed on the same frothing basis as pine oil, a well known standard frother.

The standard water-frothing test (see the penultimate item of Table I of specification) shows that 0.015 gram suflices to start good froths, and 0.025 gram were needed to make the froths run over. Triethoxybenzene is a great deal stronger than the trimethoxybenzene,

It is noted that 1,2,3 triethoxybenzene has a melting EXAMPLE 2 Pyritic ore The material treated is a cyanide slime plant residue: the flotation problem is to concentrate as much pyrites as possible, as quickly as possible, in a concentrate of as high a grade as possible, with the lowest possible consumption of frothing agent. Pulp density was approximately 36% solids; the machine used a 2000-gram Fahrenwald; conditioning agents H2804 to give a pH of 5.3, CuSO4 as a cyanicide; promoting agent 0.10 lb. per ton of sec. butyl xanthate; and frothig'agent a 5% solution of the 1,2,3 triethoxybenzene in absolute ethyl alcohol.

The addition of 0.015 lb. triethoxybenzene per dry ton of ore gave a concentrate, 10.59% by weight, assaying 36.11% sulphur, and containing 91.9% of the pyrites originally present in the ore. Period of flotation 3 minutes.

Addition of a further 0.015 lb./ton gave a middling, 2.06% by weight, assaying 7.62% sulphur, and containing a further 3.8% of the pyrites originally present in the ore. Period of flotation a further 5 minutes.

The tailings, 87.35% by weight, assayed 0.204% sulphur, and contained 4.3% of the pyrites originally present in the ore.

The froths were desirably active and rather brittle.

EXAMPLE 3 Control test with commercial 1,1,3 trieihoxybutane The run was made as in Example 2 above.

The corresponding figures were: Addition of 0060 lb. of triethoXybuta'ne/ton gave a concentrate 14.54% by weight, assaying 28.42% sulphur, and containing 93.0% of the original pyrites. Flotation time'is 3 minutes. Then, without further addition of frother, the middling, 2.31% by weight, assayed 4.04% sulphur, and contained a further 2.1% of the pyrites. Flotation time, a further 5 minutes. The tailings, 83.15% by weight, assayed 0.261% sulphur, and contained 4.9% of the original pyrites.

EXAMPLE 4 Comparison with Dowfroth 250 1,2,3 trimethoxybenzene is compared with Dow froth 250, one of the best flotation agents available at the present time for the flotation of lead-zinc ore. In this type of ore it is desirable to produce a brittle froth and it is important that the action be fast and selective.

1,2,3 trimethoxybenzene is identified as No. 4 frother below.

No. 4 frother is a solid consisting of slightly amber colored crystals, soluble in hot water. A 0.5 solu tion is made up and used for the flotation tests. In this form its action is fast and it forms a fine brittle froth of good depth, and is maintained to the end of the float. On one or two floats the froth produced was too brittle and the froth bed was shallower than normal. Flotation results are good Comparative flotation tests were made using standard test procedure. Floats were made at a pulp temperature of 20 C.

No. 4 FROTHER USED, AVE. OF 0 TESTS Percent Assays Percent Distribution Percent I Pb Zn Fe Pb Zn Fe 8. 7 41.0 13.8 15.8 82.4 22. 5 G. 8 8. 8 4. 3 41. 0 15. 4 S. 8 68. 7 0. S Tails 82. 5 (l. 46 0.57 21.0 8.8 8.8 80. 4

Products..- 100.0 4 3' 5.3 20.0 100.0 100.0 100. 0

Reagents, lbs/ton Mill Pb Float Zn Float Total Frother N0. 4.... Z9

Time, min TIeImperatm'e, "O

STANDARD TEST FOR COMPARISON, AVE. OF 6 No. 4 frother shows good properties in the flotation of this ore and is superior to Dow froth 250.

EXAMPLE 5 Tests are carried out in rigidly standardized conditions using the well known promoting reagent 301 at a natural pH of 8.0 in a standard 2,000 gram Denver- Fahrenwald flotation machine.

The ore used contained 150 lbs. per ton pyrrhotite and 13 lbs. per ton of chalcopyrite and contained a rather unusually large proportion of reactive true colloid.

Standard tests using pine oil as frother have given very poor results.

8 It is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made in the form, composition and arrangement of the ingredients without 5 departing from the spirit and scope of the invention or sacrificing its material advantages, the forms hereinbefore described being merely preferred embodiments thereof.

What is claimed is:

1. A method for concentrating minerals by flotation comprising adding to the mineral pulp a small quantity of a polyalkoxy substituted benzene as a frother, the alkoxy groups being connected to the benzene nucleus by a CO-C ether linkage and alkoxy being selected from the group consisting of methoxy, ethoxy, normal propoxy, isopropoxy, methoxy-ethoxy and ethoXy-ethoxy and thereafter subjecting the resulting mixture to a flota tion operation.

2. A method for concentrating minerals by flotation comprising adding to the mineral pulp a small quantity of a dialkoxy substituted benzene as a frother, the alkoxy groups being connected to the benzene nucleus by a C-OC ether linkage and alkoxy being selected from the group consisting of methoxy, ethoxy, normal propoxy, isopropoxy, methoxy-ethoxy and ethoXy-ethoxy and thereafter subjecting the resulting mixture to a flotation operation.

3. A method for concentrating minerals by flotation comprising adding to the mineral pulp a small quantity of a trialkoxy substituted benzene as a frother, the alkoxy groups being connected to the benzene nucleus by a C-OC ether linkage and alkoxy being selected from the group consisting of methoxy, ethoxy, normal pro- TABLE II lstandardised, strictly comparative, flotation tests in a 2,000-gram Denver-Fahrenwald machine, on a gold, chalcopyrite, pyrrllotite ore assaying approximately 16.8 dwts. Ace. as stated, at start. 2 minutes iroths designated as First Cons. designated as Second Cons.

Grind minutes with 4 grams lime and 0.30 grams copper sulphate.

Then 0.25 gram of the same xanthate, and the frother as stated. Residual pulp washed out of machine, designated as Tailings.]

0.10 gram sodium-sec. butyl xanthate and the Frother 5 minutes froths Products, Percent Weight Assays of Products Units of Sulphur (percent X Percentage of Total Cal.

assay) Sulphur Percent Test No. Sulphur Dwt.

1st 2nd Tailings Gold Tailings 1st 2nd 151; 2nd Cons. Cons. I t 2nd 'Iailings Cons. Cons. Tailings Ore Cons. Cons. Tailings s Cons. Cons.

TABLE III Quantity of Substance added Test No. Substance used as Frother (in Remarks Table II) 1st Con. 2nd Con. Total Grams Grams Grams PXX 5 122:3:5 Tetrarnethoxybcnzene..- .05 .10 15 Bottle warmed, added as liquid drops. Disperses rather slowly,

like Pine Oil. Strong deep active, froths, not watery. PXX 7 1:2:3 Trimethoxybenzenc .046 .068 114 Crystals dissolved in absolute alcohol for ease of measuring. (Weight (1) to 1 volume.) Very good active forths. Persistent. ZPXX 8 123:5 Trimethoxybcnzenc .070 .189 .259 Crystals dissolved in alcohol, 19% W./v. Clearly much weaker than previous test PXX.7. But froths of an exceptionally good type: strong, active, persistent.

TABLE IV {Standard Flotation Tests on a Chalcopyritc-Pyrrhotite Ore in a 2,000 gram Lab. machine] Mineral Grade of Products Lbs. Mineral Per Ton Ore Substance used as Frother Product, Pierocent Weight Froth Type Chalco- Pyrrho- Gangue Chal. Pyrr.

pyrite tite 1stdCmc.. 80 1g. 5 2 3 10.? 36.; 211 one .41 8 1 2 0 58. XA 1, 2, 3 Tn-Methosybenzene (0.068 g. Comb Gone 8 21 57.8 35. 6 11. 0 95.0 Very gocdpers1stcnt. Residue e1. 79 0.06 2.17 1.1 39.8 Cale. Ore- 0. 60 6. 74 12. 1 134. 8

poxy, isopropoxy, methoxy-ethoxy and ethoxy-ethoxy 6. A process as in claim 3 wherein the frother is triand thereafter subjecting the resulting mixture to a flotaethoxy benzene.

tion operation. 7. A process as in claim 4 wherein the frother is tetra.-

4. A method for concentrating minerals by flotation ethoxy benzene.

comprising adding to the mineral pulp a small quantity 6 8. A process as in claim 1 wherein the frother is a of a tetraalkoxy substituted benzene as a frother, the mixture of diiferent polyalkoxy benzenes.

alkoxy groups being connected to the benzene nucleus y a ether. p and y selectei References Cited in the file of this patent rorn t e group consisting 0 met oxy, et oxy, norma propoxy, isopropoxy, methoxy-ethoxy and ethoxy-ethoxy 10 UNITED STATES PATENTS and thereafter subjecting the resulting mixture to a flota- 1,902,070 Halbig Mar. 21, 1933 tion operation. 2,561,251 Van Aardt July 17, 1951 5. A process as in claim 2 wherein the frother is di- 2,591,289 Powell et a1. Apr. 1, 1952 ethoxy benzene. 

1. A METHOD FOR CONCENTRATING MINERALS BY FLOTATION COMPRISING ADDING TO THE MINERAL PULP A SMALL QUANTITY OF A POLYALKOXY SUBSTITUTED BENZENE AS A FROTHER, THE ALKOXY GROUPS BEING CONNECTED TO THE BENZENE NUCLEUS BY A C-O-C ETHER LINKAGE AND ALKOXY BEING SELECTED FROM THE GROUP CONSISTING OF METHOXY, ETHOXY, NORMAL PROPOXY, ISOPROPOXY, METHOXY-ETHOXY AND ETHOXY-ETHOXY AND THEREAFTER SUBJECTING THE RESULTING MIXTURE TO A FLOTATION OPERATION. 